Regular Article

First principles electron-correlated calculations of optical absorption in magnesium clusters^★

¹ Materials Research Center, Indian Institute of Science, Bangalore, Karnataka 560012, India
² Department of Physics, Indian Institute of Technology Bombay, Mumbai, Maharashtra 400076, India

^a e-mail: ravindra@mrc.iisc.ernet.in

Received: 27 May 2017
Received in final form: 29 August 2017
Published online: 23 November 2017

Abstract

In this paper, we report large-scale configuration interaction (CI) calculations of linear optical absorption spectra of various isomers of magnesium clusters Mg_n (n = 2–5), corresponding to valence transitions. Geometry optimization of several low-lying isomers of each cluster was carried out using coupled-cluster singles doubles (CCSD) approach, and these geometries were subsequently employed to perform ground and excited state calculations using either the full-CI (FCI) or the multi-reference singles-doubles configuration interaction (MRSDCI) approach, within the frozen-core approximation. Our calculated photoabsorption spectrum of magnesium dimer (Mg₂) is in excellent agreement with the experiments both for peak positions, and intensities. Owing to the sufficiently inclusive electron-correlation effects, these results can serve as benchmarks against which future experiments, as well as calculations performed using other theoretical approaches, can be tested.